半乳糖-聚乙二醇-聚-L-赖氨酸共聚物的制备与分析

 将相对分子质量为4 000的聚乙二醇中活性较弱的羟基转化为氨基，利用乳糖分子中含有半缩醛结构，可与双端氨基聚乙二醇（AT-PEG）分子中的伯氨基形成Schiff 碱，然后在氰基硼氢化钠作用下选择性还原为稳定的C-N 单键，使半乳糖连接在PEG的一个氨基上，合成半乳糖-单端氨基聚乙二醇（Gal-PEG-NH₂），以Gal-PEG-NH₂为大分子引发剂，引发N^ε-苄氧羰基-L- 赖氨酸-N-羧酸酐［Lys(Z) NCA］开环聚合制备一系列半乳-糖-聚乙二醇-聚-L-赖氨酸（PLL-PEG-Gal）嵌段共聚物，通过调节Lys(Z) NCA和 Gal-PEG-NH₂的摩尔比例（［A］/［I］）可控制聚合物的相对分子质量。利用IR、¹³C-NMR、UV等方法进行共聚物结构分析，并对其接糖率进行了分析。结果表明，乳糖与双端氨基聚乙二醇反应生成的带有一侧氨基的聚乙二醇能引发Lys(Z) NCA 聚合生成Gal-PEG-PLL，其中半乳糖的接入率为8.3%。随着［A］/［I］的增加，共聚物的相对分子质量变大。

Synthesis and Characterization of Block Copolymers of Galactose-polyethyleneglycol-poly(L-lysine)

Amino terminated polyethylene glycol with 4 000 molecular weight was synthesized using the method of toluenesulfonate esterification.Amine terminated poly(ethylene glycol) galactose(Gal-PEG-NH₂) was then synthesized by conjugating the hemiacetal groups of lactose and the primary amine groups of PEG-bis(amine) in 0.1 mol/L sodium tetraborate buffer at pH 9.0 for 48 h using sodium cyanoborohydride.A series of block copolymers of galactose-polyethyleneglycol-poly(L-lysine)(Gal-PEG-PLL) with different molecular weights were finally synthesized through the ring-opening polymerization of Lys(Z) NCA initiated by galactose-PEG-NH₂.Their structures were characterized by IR，¹³C NMR and UV analyses.The results confirmed the expected block structures.The block contents and number-average molecular weights of the copolymers were adjusted by changing the feeding ratio of Lys(Z) NCA to macroinitiator.The content of galactose in copolymer reached 8.3%.